The present invention relates to a proportional variable force solenoid operated valve that controls fluid pressure in response to electrical current applied to a valve solenoid and, more particularly, to a proportional variable force solenoid operated valve having armature damping means to improve valve response stability to pressure oscillations in the controlled fluid system.
A proportional variable force solenoid control valve that is relative low in cost to manufacture and compact in size while maintaining substantially linear proportional fluid control is described in the Najmolhoda U.S. Pat. No. 4,988,074 issued Jan. 29, 1991, of common assignee herewith. The patented proportional varaible force solenoid control valve comprises an outer steel solenoid housing and an aluminum valve member housing joined together mechanically such as by tabs on the steel solenoid housing being crimped about regions of the aluminum valve member housing.
The proportional variable force control valve includes a ferromagnetic (e.g. steel) armature suspended by low spring rate springs at opposite ends of the armature within the bore hole of a coreless solenoid bobbin for reciprocable movement between positions corresponding to a closed valve position and fully open valve position in response to applied electrical current to an electromagetic coil. The position of the armature is controlled by balancing the variable force of an electromagnetic field of an electromagnetic coil and the force of the magnetic field of a permanent ring magnet against the force of a compression coil spring which biases the valve toward the closed position of the valve. The electromagnetic coil, bobbin and armature reside in the steel solenoid housing in a manner that the steel housing provides a concentration of flux of the electromagnetic field at the armature. The fluid control valve on the end of the armature moves relative to a valve seat disposed in the aluminum valve housing to communicate a fluid inlet to fluid exhaust ports so as to regulate fluid pressure at fluid control ports in a manner proportional to the magnitude of applied electrical current.
A commercially manufactured version of the aforementioned patented proportional variable force solenoid fluid control valve has been modified to include a stainless steel ball valve and a separate stainless steel valve seat insert pressed in the nozzle. The ball valve is captured in a stainless steel cage between the valve seat and a rod-like, cylindrical shaped steel armature that moves relative to the valve seat in a manner proportional to the magnitude of electrical current applied to the electromagnetic coil. As the armature moves relative to the valve seat to actuate the valve, the ball valve is caused to follow the end of the armature by virtue of fluid pressure in the valve member housing and confinement in the ball valve cage in the bobbin. The fluid inlet is communicated to fluid exhaust ports by opening of the ball valve so as to regulate fluid pressure at fluid control ports in a manner proportional to the magnitude of electrical current applied to the coil.
A spool valve is disposed in the valve member housing for providing a two stage, high flow capability wherein pressurized fluid supplied to the inlet port initially is directed to bypass the control ports and flows to an end of the spool valve to move it from a zero fluid flow spool position to a maximum fluid flow spool position relative to the control ports as determined by the cracking pressure preset for the ball valve by adjustment of the coil spring force. Thereafter, a second stage of operation involves controlling the fluid flow through the control ports by moving the spool valve between minimum and maximum flow spool positions in a manner proportional to the magnitude of electrical current to the coil. Such proportional variable force solenoid control valves commercially manufactured to-date are operably mounted to a cast aluminum transmission body or case by a clamp plate, bolt, or both engaging an outer nozzle groove. The Najmolhoda U.S. Pat. No. 5,611,370 issued Mar. 18, 1997, also describes a proportional variable force solenoid control valve that includes a substantially non-magnetic common housing for the solenoid and control valve, simplfying valve manufacture and construction while maintaining substantially linear proportional fluid pressure control.
In use of the proportional variable force solenoid pressure control valve in an electronically controlled automatic transmission of an automobile or other complex hydraulic control system, there are many sources of hydraulic and/or electromechanical xe2x80x9cnoisexe2x80x9d in the controlled fluid system, which can initiate or aggravate system instability by causing a sympathetic harmonic vibration in related system components. System hydraulic vibrational instabilities can create detrimental valve performance characteristics which affect vehicle performance or reliability. In an automatic transmission, the proportional variable force solenoid pressure control valve usually controls many critical system parameters and its performance should be consistent and stable. When a pressure control solenoid responds to the inherent electronic and/or hydraulic system noise by being forced into an uncontrolled vibration response, the entire fluid system may become unstable.
An object of the present invention is to provide a proportional variable force solenoid fluid control valve and method having improved valve response stability to noise in the controlled fluid system, especially in use in an electronically controlled hydraulic automatic transmission application.
Another object of the present invention is to provide a proportional variable force solenoid control valve and method having improved valve response stability to noise in the controlled fluid system by virtue of armature damping means.
The present invention provides a proportional variable force solenoid fluid control valve and method for controlling the pressure of a pressurized fluid in a fluid control system in proportion to the current level of an electrical input signal. In one embodiment of the present invention, the proportional variable force solenoid fluid control valve comprises an armature in engagement with a fluid pressure control valve and movable in response to electrical current applied to a solenoid disposed on a coil bobbin in a solenoid housing and means for biasing the armature in a direction to establish a valve fluid pressure response to current level supplied to the solenoid (i.e. fluid pressure versus solenoid current).
In accordance with an embodiment of the present invention, the armature includes or cooperates with a damping member, such as an armature damping disk connected to or engaged by an inner end of the armature, for movement therewith in a fluid damping chamber disposed proximate the inner armature end to receive the damping member in a manner to reduce or dampen pressure oscillations resulting from electrical, mechanical and/or hydraulic noise in the controlled fluid system or circuit, thereby improving valve response stability. The cross-sectional area of the damping member and clearance between the periphery of the damping member and the cooperating wall of the damping chamber are selected to this end. The damping member may be formed integral with the armature or connected thereto, such as by press-fit. Alternately, the damping member may be separate from the armature yet engaged thereby in a manner to reduce or dampen pressure oscillations.
In one embodiment of the invention, the damping chamber is disposed in a valve or nozzle housing proximate fluid exhaust ports, although the invention is not limited in this regard.
The damping member may be made of a magnetically permeable material, such as steel, to provide an improved magnetic flux carrier to direct magnetic flux directly into the armature, while reducing size of the solenoid unit, although the invention is not limited in this regard.